Journal Article

Two breakthrough gene-targeted treatments for spinal muscular atrophy: challenges remain

Sumner, Charlotte J., Crawford, Thomas O.

2018

Overview

The motor neuron disease spinal muscular atrophy (SMA) is caused by recessive, loss-of-function mutations of the survival motor neuron 1 gene (SMN1). Alone, such mutations are embryonically lethal, but SMA patients retain a paralog gene, SMN2, that undergoes alternative pre-mRNA splicing, producing low levels of SMN protein. By mechanisms that are not well understood, reduced expression of the ubiquitously expressed SMN protein causes an early-onset motor neuron disease that often results in infantile or childhood mortality. Recently, striking clinical improvements have resulted from two novel treatment strategies to increase SMN protein by (a) modulating the splicing of existing SMN2 pre-mRNAs using antisense oligonucleotides, and (b) transducing motor neurons with self-complementary adeno-associated virus 9 (scAAV9) expressing exogenous SMN1 cDNA. We review the recently published clinical trial results and discuss the differing administration, tissue targeting, and potential toxicities of these two therapies. We also focus on the challenges that remain, emphasizing the many clinical and biologic questions that remain open. Answers to these questions will enable further optimization of these remarkable SMA treatments as well as provide insights that may well be useful in application of these therapeutic platforms to other diseases.

• Publisher: American Society for Clinical Investigation
• Subject: Age / Alternative splicing / Analysis / Antisense oligonucleotides / Antisense RNA / Atrophy / Biomedical research / Care and treatment / Children / Clinical trials / Dependovirus / Gene expression / Gene Targeting - methods / Gene therapy / Humans / Medical screening / Motor neuron diseases / Motor neurone disease / Motor Neurons - metabolism / Motor Neurons - pathology / mRNA / Muscular Atrophy, Spinal - genetics / Muscular Atrophy, Spinal - metabolism / Muscular Atrophy, Spinal - therapy / Musculoskeletal system / Mutation / Neuromuscular diseases / Oligonucleotides, Antisense - genetics / Oligonucleotides, Antisense - therapeutic use / Patients / Proteins / Review / Risk factors / RNA splicing / RNA Splicing - genetics / SMN protein / Spinal muscular atrophy / Survival of Motor Neuron 1 Protein - genetics / Survival of Motor Neuron 1 Protein - metabolism / Survival of Motor Neuron 2 Protein - genetics / Survival of Motor Neuron 2 Protein - metabolism / Vectors (Biology)